Dark and Light

When Warner Bros.’ Batman Begins appeared on screen in 2005, audiences saw director Christopher Nolan’s vision of superhero movies for the first time, a dark vision in which gritty digital effects melted into realistic backgrounds. Famous for wanting to capture everything in camera, Nolan challenged the VFX teams to produce invisible effects. The film earned visual effects BAFTA nominations in 2006 for special effects supervisor Chris Corbould and visual effects supervisors Paul Franklin, Janek Sirrs, and Dan Glass.

But that movie’s success paled next to his sequel, The Dark Knight. This time, to heighten the visual impact, Nolan filmed several sequences with high-resolution, 65mm IMAX cameras, which sent huge amounts of data through the digital effects studios’ pipelines. For that feature, writer/director Nolan again placed the deeply troubled caped crusader in dark chaos and a bleak, unsentimental location, and again, the effects, while spectacular, never upstaged the characters. The Dark Knight smashed opening weekend records, achieved a 94 percent approval from critics according to reviews aggregated on Rotten Tomatoes, and eventually earned more than $1 billion worldwide. Corbould and Franklin received Oscar nominations for the film, and followed Nolan onto his next movie, Inception, for which they won Oscars for best visual effects. And for his part, Nolan received two Oscar nominations, for best picture and best original screenplay.

So, it’s no wonder that Nolan brought back Corbould, Franklin, and cinematographer Walley Pfister (who won an Oscar for Inception) to help him realize the last film in the trilogy, Warner Bros.’ The Dark Knight Rises. This time, Nolan and his brother Jonathan, who helped write The Dark Knight and other films, sent Batman to war in the streets of New York City. There are epic battles, extraordinary effects, and, once again, rough-hewn reality.

(Above) Double Negative created many of the buildings in Gotham City using 3D models.

High-Res Heroics
“Chris [Nolan] always challenges everyone on his shows to bring their best to the movie,” says visual
effects supervisor Paul Franklin. “Whatever we did last time, he’s looking to go one better this time.” Going one better for this film was not a trivial task. After the previous two features, Nolan was more convinced than ever to film in high resolution, and after the last three films, he had become more comfortable with visual effects.

“I think we had about 24 minutes of film shot on 65mm IMAX, the same format we had used for Dark Knight,” Franklin says, “5.6k x 4k resolution. But we had 25 minutes of IMAX then. This film has close to an hour. We shot the rest of the film in cinemascope at 4k.” Double Negative was one of four vendors on Dark Knight, but on Dark Knight Rises, all visual
effects shots ran through that studio.

“I think that of about 450 visual effects shots, approximately 350 were IMAX,” Franklin says. “We set aside 250tb of online storage for the film, a quarter of a petabyte. We ended up with close to half a petabyte. It required an industrial-strength operation, but disk space is cheaper now and computers are faster. And, we’re using Nuke from The Foundry, which is great at handling large resolution compared to [Apple’s] Shake. We have a lot of custom software built around it: plug-ins, shot management tools.”

The bulk of Double Negative’s work centered on a football stadium sequence and a final chase sequence through Gotham City, but among the 450 shots, the studio also helped create an aerial heist, built a flying vehicle, blew up bridges, extended a prison, and generated a colony of bats.

“I think that after Dark Knight and Inception, Chris learned he could rely on visual effects to carry story points,” Franklin says. “So on this film, sometimes I didn’t want to go down a VFX route, and he’d say, ‘We’ll use visual effects.’ In New York City, for example, there were limitations about what we could do in the streets, so to create some of the bigger moments, we had to turn to visual effects, particularly on the bridges.”

Early in the film, the villain Bane blows up the bridges to isolate Gotham City. Double Negative created those scenes digitally, as well as a replica of the one remaining bridge that Bane keeps open. “We had to make a very accurate digital model of the 59th Street Bridge, the Queensborough Bridge,” Franklin says. “It’s a complicated latticework structure, so we had the guys do a Lidar scan and survey it extensively. They had let us shut down the upper deck of the bridge for filming, but the lower deck had traffic. Sometimes it’s easier to use a CG bridge, and our bridge fit in nicely.”

The audience meets Bane during an aerial heist, which the film crew shot over the Highlands in Scotland. Stunt coordinator Tom Struthers dropped four skydivers on wires from a C-130 Hercules transport plane. In the final shot, they land on a smaller, turboprop plane and attach cables from the small plane to the large plane. “We see the small plane dangling from the wire like a fish,” Franklin says. “We created the shot with a digital small plane and a miniature. As the digital plane is being hoisted up, the wings start vibrating.” Then, at New Deal Studios, the wings break away from a one-fifth scale miniature shot on greenscreen that Double Negative artists enhanced with digital effects.

Inside the plane, the actors tumble around thanks to a set built by Corbould’s team that could tilt 90 degrees, yaw, and roll. Double Negative artists helped make the shot seem believable by creating a digital environment visible through the windows.

“The skydivers attach chargers, blow off the tail, and crack the plane open like an egg to get to Bane and his henchman inside,” Franklin says. “In Scotland, they had the fuselage of a plane attached to a helicopter. We tracked in a CG piece to put the ‘cap’ back on. The cap blows off with a miniature explosion at New Deal. So, we have a real plane’s fuselage, a CG cap, and a tumbling miniature plane piece at New Deal.”

Gotham City
The visual effects teams working on the previous films had established the idea of Gotham City as a huge, modern East Coast city sprawling out of control. For Dark Knight, Chicago stood in. “Chicago provided a fantastic backdrop,” Franklin says. “But for this film, Chris [Nolan] wanted a bigger scale.”

The crews filmed a motorcycle chase in downtown Los Angeles. And, with IMAX cameras mounted on a low-riding pickup truck, the visual effects plate unit shot footage of street environments in New York City that the crew would use for background plates and CG textures. But, Pittsburgh provided the majority of material. “We digitized and modeled a whole four-city-block area of Pittsburgh,” Franklin says. “That gave us a library of buildings we could use to dress other locations, to fill in the gaps. This common library of Pittsburgh buildings provided a thematic connection between the locations.”

To collect HDRI images of these locations and the sets, the crew used a proprietary camera system. “We have four digital SLRs mounted in a case on a tripod that point to the four points of the compass,” Franklin says. “Each has a fish-eye view so we can capture overlapping fields of view. We connect the cameras to a laptop. Software brackets the photographs and assembles them into panoramas that describe the lighting and the environment.”

As soon as they had captured the HDRI panoramas and other reference photography on set, the crew sent the images to the look development artists at Double Negative, so the team could begin building assets and environments. “By the time shooting wrapped in November, they had all the assets ready to go,” Franklin says. “That was important because we never have much time to do these things and Chris’s postproduction is always tight. But, I was prepared for that.”

The modelers designed most of the buildings in the Gotham library based on Pittsburgh structures and used those to extend streets in a chase sequence and to replace buildings as needed. During the Pittsburgh chase, Batman pursues the villains, who are riding in a huge, 12-wheeled truck, with his new vehicle. “People called it a ‘Batwing,’ or sometimes just the ‘Bat,’ ” Franklin says. “It is an incredible flying vehicle and perhaps our biggest challenge.”

Flying into Reality
Corbould’s team built a full-size version of the Bat and mounted it on a hydraulic crane on a four-wheeled motion base. “There was a car underneath it,” Franklin says. “They had three operators: one to drive, one to operate the pitch, and one to control the hydraulic arm. It was an impressive thing to see. It thundered down the street at 40 to 50 miles per hour. They could drive it in a straight line and swerve down the street, but it wasn’t so good going around corners, and it couldn’t fly.”

The hydraulic arm could push the Bat upward 10 or 12 feet on location. Later, to make it look like it was flying, the artists at Double Negative painted out the support vehicle and hydraulic arm. But, when the Bat really needed to maneuver, the digital artists took the wheel of a CG machine.

In the shot, Bane’s forces have taken control of various military vehicles that Wayne enterprises had built, and they use these to fire heat-sensing missiles at the Bat. “Batman has to take off in an aerial sequence, weaving through the streets and around the rooftops to evade the missiles,” Franklin says. “We couldn’t use the physical machine up there.”

For these shots, Double Negative artists inserted the CG Bat into backgrounds composited from aerial plates shot in Pittsburgh and New York. “They matched perfectly,” Franklin says. “The team at Double Negative came up with a fantastic new system based on [Pixar’s] RenderMan 16 with custom shading, and our own lighting tools in a system we call Rex. The physically-based renderer correctly calculates bouncing and the conservation of energy as light rays bounce around the scene.”

Previously, to fit a digital Batmobile into scenes for Dark Knight, the artists graded each surface of the vehicle. “We judged everything by eye,” Franklin says. “Does this match the reference shadows? Are the highlights too hot?”

For this film, the combination of [HDRI] lighting maps, reference photography, rendering software, and artistic skill gave Franklin digital vehicles that behaved in a consistent manner. “We could give the rendering team an animation, and a render would come back the next day that was a pretty seamless match without any secondary grading,” he says. “It was a huge time-saver. I might say an object needed to be brighter or darker, but I didn’t have to grade each surface of the object.”

The impact rippled beyond convenience. “It meant we could spend more time on the movement and believability of the vehicle, rather than thinking about the nuts and bolts that go into making sure it is realistically lit,” Franklin says. “It meant we could say to Chris [Nolan], ‘I can bring this thing right into camera at full resolution, have it linger there, and it will look good.’ And, it gave Chris the confidence that we could pull off the high-resolution, complicated things he had filmed. The big climactic scenes are in full daylight in this film, so we really pushed our rendering and lighting to the full limit.”
Explosive Details
One of the biggest sequences involving digital visual effects takes place in the Pittsburgh Steelers’ Heinz Field, which stars as Gotham Stadium in the film. Given Nolan’s propensity to film everything in camera, he persuaded 15,000 people to dress in winter clothes in the middle of the summer and sit in the stands. That worked for some shots, but there weren’t enough fans to fill the 65,000-capacity stadium for the wide shots of the field exploding.

“We extended the crowds digitally through a combination of elements shot against greenscreen and with a custom crowd system,” Franklin says. “But, the key thing was the collapse of the stadium. I suggested that we do a miniature, knowing Chris likes that sort of thing, and miniatures worked well for us on Inception, but he felt that using a miniature wouldn’t be precise enough. The explosion starts slowly at the back and comes to the edge of a man running. So we went with a digital solution.”

The team at Double Negative built an entire CG stadium, including all the underground levels beneath the field. Then, using a combination of proprietary tools, Side Effects’ Houdini and Autodesk’s Maya, they created a rolling, tightly choreographed wave of destruction. “The physics simulations were very complicated,” Franklin says. “We used an awful lot of in-house solvers. The system was an evolution of the system we created for Inception to collapse the buildings by the seafront, but this was an order of magnitude more complicated. We had to show destruction in a wide shot from the whole of the field, which was hundreds of yards wide, to literally five feet from the camera. The detail increased as the shot progressed. Then, we had to show it from multiple angles, as well.”

Thus, they couldn’t create the simulation from one camera’s view; they had to create a solution viewable from all angles.

“We started by previsualizing the sequence,” Franklin says. “Chris had always been skeptical about previs, but this time around, our previs team laid out the timing used to choreograph the stunts on the day. It was so complicated. We got all the department heads together and decided what would be stunts, what would be practical, what would be visual effects, and came to an agreement.”

The simulation artists also created the fire, smoke, and building destruction, after an explosion that happens toward the end of the film, using Houdini, Maya fluids, and the studio’s in-house fluid system, called Squirt. Modelers extended a massive prison set in a huge well. In addition, the team modeled, animated, and rendered a colony of bats. “They explode out of the well and startle Batman,” Franklin says. “We re-created the same species that was in Batman Begins, the Egyptian free-tailed bat. But because they would be in IMAX resolution, we added details.”

The need to add detail was consistent throughout the film, from vehicle, to building, to fire and smoke, but this team had met the challenge before. “In terms of working on the film, it felt familiar because we’ve maintained many of the same people since 2003,” Franklin says. “This is our fourth film, so we had a real sense of continuity. On Dark Knight, we were feeling our way, working at this incredibly high resolution. But a lot of the people who came back for this film knew what we were getting into.”

Franklin believes the result of their combined experience has lifted the state of the art of visual effects once again. “We pushed the believability of our CG-generated environments and vehicles,” he says. “And, in daylight. They fit in seamlessly with photography. I think that was particularly extraordinary with the Bat and the stunts we replaced. When you watch the film, it looks like it was all shot for real, and that’s the goal.
Although computers have gotten faster, which makes dealing with the increased amount of data much easier, and software tools have gotten better, especially compositing and rendering tools, Franklin attributes the success of this film to the skills of the artists.

“They’ve gotten better and better,” Franklin says. “The tools get more powerful and faster, but it’s the artists’ skills that make the difference. The people on our team fully understand the world that Chris tries to create with his films, and that produces astonishing results.”

Barbara Robertson is an award-winning writer and a contributing editor for Computer Graphics World. She can be reached at BarbaraRR@comcast.net.